README: add info and fix typos

[CaitinChen]

What problem does this PR solve?

add info and fix typos

What is changed and how it works?

add info and fix typos

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release notes:

NONE

[CLAassistant]

All committers have signed the CLA.

[CaitinChen]

@lilin90 PTAL

[codecov-io]

Codecov Report

Merging #1095 (86398e9) into master (8dfd3fa) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1095      +/-   ##
==========================================
- Coverage   56.66%   56.63%   -0.03%     
==========================================
  Files         283      283              
  Lines       20045    20045              
==========================================
- Hits        11358    11353       -5     
- Misses       6934     6936       +2     
- Partials     1753     1756       +3     

Flag	Coverage Δ
cluster	45.09% <ø> (-0.07%)	⬇️
dm	24.91% <ø> (+0.06%)	⬆️
integrate	51.04% <ø> (-0.03%)	⬇️
playground	20.89% <ø> (ø)
tiup	16.36% <ø> (+0.02%)	⬆️
unittest	22.79% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/utils/http_client.go	67.56% <0.00%> (-5.41%)	⬇️
pkg/cluster/manager/manager.go	65.38% <0.00%> (-3.85%)	⬇️
pkg/cluster/api/pdapi.go	58.67% <0.00%> (-1.90%)	⬇️
pkg/cluster/api/dmapi.go	60.00% <0.00%> (+1.73%)	⬆️
pkg/repository/store/txn.go	62.01% <0.00%> (+2.32%)	⬆️

---

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[lucklove]

/lgtm

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lucklove

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[nrc]

lgtm

[lilin90]

Suggested change

	- [English](https://www.pingcap.com/blog/)
	- [English](https://pingcap.com/blog/)

[lilin90]

/lgtm

[ti-chi-bot]

@lilin90: /lgtm is only allowed for the reviewers in list.

In response to this:

/lgtm

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[lucklove]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 86398e9